The present invention relates to a method for manufacturing a semiconductor device. More particularly, the present invention relates to a method for manufacturing a semiconductor device using a tungsten nitride thin film.
The reliability and efficient formation of metal wiring and other metal structures within a semiconductor device largely determine the speed with which the device will operate, the manufacturing yield for the device, and its overall reliability. Accordingly, the method by which metal wiring and other metal structure are formed in a semiconductor device is among the most critical within the sequence of methods used to manufacture the device.
In early semiconductor devices having a relatively lower integration density, step coverage for a metal wiring layer did not pose much of a problem. Typically, aluminum (Al) has been used to form metal wiring layers. However, continuing increases in the integration of semiconductor devices have resulted in the necessity of forming contact holes with much smaller diameters, down to half micron. This necessity has proved problematic, since conventional methods of forming the metal wiring using Al can not reliably form buried contact holes having a diameter less than 1 .mu.m. Attempts to use conventional Al methods in the formation of sub-1 .mu.m contact holes often results in the formation of voids which adversely affect the reliability of the semiconductor device.
One conventional method of forming contact holes suggests using an aluminum and 1% silicon compound in which Al is over-saturated with silicon. Formation of a metal wiring layer from this compound typically requires that a barrier metal layer be formed between the metal wiring layer and the silicon substrate or insulating layer in order to prevent the formation of Al spiking, Si residue, or Si nodule caused by a reaction between the metal wiring layer and the silicon substrate. FIG. 1 is a sectional view illustrating this method of forming a metal wiring in a semiconductor device.
In FIG. 1, an active region is defined by a selectively formed field insulating film 3 in a semiconductor substrate 2. After forming an impurity diffusion region 4 which becomes a source/drain region in the active region, an insulating layer 6 having a contact hole exposing a portion of the impurity diffusion region 4 is formed. A barrier metal layer of titanium (Ti) 8 and titanium nitride (TiN) 10 is formed on side and bottom surfaces of the contact hole using a sputtering method. An Al metal wiring layer 12, which buries the contact hole, is then formed over TiN layer 10 to complete the exemplary electrode structure.
In this conventional method of forming metal wiring, the barrier metal layer is formed by a sputtering technique. This being the case, step coverage for the barrier metal layer becomes increasingly inferior as the aspect ratio of the contact hole increases. As step coverage degrades, voids are formed which short circuit th e electrical connection between the metal wiring and the underlying impurity diffusion region. Reliability of the semiconductor device suffers accordingly.
In addition to the foregoing problem, the TiN film used in the conventional barrier metal layer has a columnar structure. As such, TiN is not particularly well suited to its purpose in the foregoing structure. In fact, a subsequent heat treatment step is typically performed to reinforcing a TiN film structure. This additional step adds manufacturing complexity and can result in adverse side effects.